A narrowly endemic photosynthetic orchid is non‐specific in its mycorrhizal associations

Abstract

Mycorrhizal association is a common characteristic in a majority of land plants, and the survival and distribution of a species can depend on the distribution of suitable fungi in its habitat. Orchidaceae is one of the most species-rich angiosperm families, and all orchids are fully dependent on fungi for their seed germination and some also for subsequent growth and survival. Given this obligate dependence, at least in the early growth stages, elucidating the patterns of orchid-mycorrhizal relationships is critical to orchid biology, ecology and conservation. To assess whether rarity of an orchid is determined by its specificity towards its fungal hosts, we studied the spatial and temporal variability in the host fungi associated with one of the rarest North American terrestrial orchids, Piperia yadonii. The fungal internal transcribed spacer region was amplified and sequenced by sampling roots from eight populations of P. yadonii distributed across two habitats, Pinus radiata forest and maritime chaparral, in California. Across populations and sampling years, 26 operational taxonomic units representing three fungal families, the Ceratobasidiaceae, Sebacinaceae and Tulasnellaceae, were identified. Fungi belonging to the Sebacinaceae were documented in orchid roots only at P. radiata forest sites, while those from the Ceratobasidiaceae and Tulasnellaceae occurred in both habitats. Our results indicate that orchid rarity can be unrelated to the breadth of mycorrhizal associations. Our data also show that the dominance of various fungal families in mycorrhizal plants can be influenced by habitat preferences of mycorrhizal partners.

Habitat-driven variation in mycorrhizal communities in the terrestrial orchid genus Dactylorhiza

“…Recent studies have shown that orchid mycorrhizal communities can vary substantially between species within sites611. In a similar way, mycorrhizal communities have been shown to vary between sites within species1213. In this case, variation in mycorrhizal communities was significantly driven by variation in environmental conditions, which suggests that local growth conditions can impact on fungal communities.…”

New species of Tulasnella associated with terrestrial orchids in Australia

“…Indeed, numerous molecular OTUs have been designated amongst Tulasnella associated with orchids (e.g. Smith et al 2010, Jacquemyn et al 2011, 2012, Pandey M et al 2013, Cruz et al 2014, Oja et al 2015) or liverworts (Kottke et al 2003, Bidartondo & Duckett 2010), without formally naming the species. Formal naming of the species is preferred and essential to prevent confusion of taxonomic units discovered in separate studies (Hibbett & Taylor 2013).…”

Identity and Specificity of Rhizoctonia-Like Fungi from Different Populations of Liparis japonica (Orchidaceae) in Northeast China

“…Our results also supported that high specificity in widespread and photosynthetic orchids may be more common than previously thought. Moreover, the phenomenon that multiple fungal taxa existed in a single root system was detected in some photosynthetic orchids which indicated that multiple fungi in a single root system may occur more often in photosynthetic than in mycoheterotrophic orchids [26]. While our results showed that this characteristic is not universal in orchid mycorrhizal systems.…”

“…The Rhizoctonia -like fungi includes members of the Ceratobasidiaceae, Sebacinales and Tulasnellaceae [15], [17]. However, the taxonomy, diversity and distribution patterns of mycorrhizal fungi may vary considerably among different orchid species or different populations within the same species, ranging from very narrow specificity to little specificity [18]–[26]. Therefore, knowing the identity of the fungi that form mycorrhizas with orchids and the specificity of the relationships are of crucial importance for orchid ecology and conservation [27].…”